/* ===== 基础变量 ===== */
:root {
    --tg-blue: #2AABEE;
    --tg-blue-dark: #229ED9;
    --tg-blue-light: #54A9EB;
    --tg-blue-gradient: linear-gradient(135deg, #2AABEE 0%, #229ED9 100%);
    --text-primary: #1f1f1f;
    --text-secondary: #5f6368;
    --text-light: #8a8d91;
    --bg-white: #ffffff;
    --bg-light: #f5f8fc;
    --bg-card: #ffffff;
    --border-color: #e8eaed;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 16px 40px rgba(42, 171, 238, 0.18);
    --radius-sm: 10px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --header-height: 72px;
}

/* ===== 重置 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: var(--header-height);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
        "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
    color: var(--text-primary);
    line-height: 1.6;
    background: var(--bg-white);
    overflow-x: hidden;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

img, svg {
    display: block;
    max-width: 100%;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

.section {
    padding: 100px 0;
}

/* ===== 按钮 ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 14px 32px;
    border-radius: 50px;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s ease;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--tg-blue-gradient);
    color: #fff;
    box-shadow: 0 8px 20px rgba(42, 171, 238, 0.35);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 28px rgba(42, 171, 238, 0.45);
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.95);
    color: var(--tg-blue-dark);
    border: 2px solid var(--tg-blue);
}

.btn-secondary:hover {
    background: var(--tg-blue);
    color: #fff;
    transform: translateY(-2px);
}

.btn-lg {
    padding: 18px 48px;
    font-size: 1.125rem;
}

.gradient-text {
    background: var(--tg-blue-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* ===== 头部 ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid rgba(232, 234, 237, 0.6);
    z-index: 1000;
    transition: box-shadow 0.3s ease;
}

.header.scrolled {
    box-shadow: var(--shadow-sm);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--text-primary);
}

.logo-icon {
    width: 36px;
    height: 36px;
}

.nav-links {
    display: flex;
    gap: 36px;
}

.nav-links a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-secondary);
    transition: color 0.2s ease;
    position: relative;
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--tg-blue-gradient);
    transition: width 0.3s ease;
}

.nav-links a:hover {
    color: var(--tg-blue-dark);
}

.nav-links a:hover::after {
    width: 100%;
}

.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
}

.menu-toggle span {
    width: 24px;
    height: 2px;
    background: var(--text-primary);
    border-radius: 2px;
    transition: all 0.3s ease;
}

.menu-toggle.active span:nth-child(1) {
    transform: translateY(7px) rotate(45deg);
}

.menu-toggle.active span:nth-child(2) {
    opacity: 0;
}

.menu-toggle.active span:nth-child(3) {
    transform: translateY(-7px) rotate(-45deg);
}

/* ===== 英雄区 ===== */
.hero {
    position: relative;
    padding-top: calc(var(--header-height) + 60px);
    padding-bottom: 80px;
    background: linear-gradient(180deg, #f5f8fc 0%, #ffffff 100%);
    overflow: hidden;
}

.hero-content {
    display: grid;
    grid-template-columns: 1.1fr 0.9fr;
    gap: 60px;
    align-items: center;
}

.hero-text h1 {
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.15;
    margin-bottom: 24px;
    letter-spacing: -0.02em;
}

.hero-subtitle {
    font-size: 1.2rem;
    color: var(--text-secondary);
    margin-bottom: 36px;
    max-width: 540px;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
    margin-bottom: 48px;
}

.hero-stats {
    display: flex;
    gap: 40px;
    flex-wrap: wrap;
}

.stat {
    display: flex;
    flex-direction: column;
}

.stat strong {
    font-size: 1.75rem;
    font-weight: 800;
    background: var(--tg-blue-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.stat span {
    font-size: 0.9rem;
    color: var(--text-light);
    margin-top: 4px;
}

/* ===== 手机 Mockup ===== */
.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.phone-mockup {
    width: 300px;
    height: 600px;
    background: #1f1f1f;
    border-radius: 44px;
    padding: 12px;
    box-shadow: 0 40px 80px rgba(42, 171, 238, 0.25),
                0 20px 40px rgba(0, 0, 0, 0.15);
    position: relative;
}

.phone-mockup::before {
    content: '';
    position: absolute;
    top: 20px;
    left: 50%;
    transform: translateX(-50%);
    width: 120px;
    height: 28px;
    background: #1f1f1f;
    border-radius: 0 0 18px 18px;
    z-index: 2;
}

.phone-screen {
    width: 100%;
    height: 100%;
    background: var(--tg-blue-gradient);
    border-radius: 32px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.chat-header {
    background: var(--tg-blue-gradient);
    padding: 50px 16px 14px;
    display: flex;
    align-items: center;
    gap: 12px;
    color: #fff;
}

.avatar {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.25);
    border: 2px solid rgba(255, 255, 255, 0.4);
}

.chat-info .chat-name {
    font-weight: 700;
    font-size: 1rem;
}

.chat-info .chat-status {
    font-size: 0.78rem;
    opacity: 0.85;
}

.chat-body {
    flex: 1;
    background: #f0f6fb;
    padding: 16px 12px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    overflow-y: auto;
}

.message {
    max-width: 75%;
    padding: 10px 14px;
    border-radius: 18px;
    font-size: 0.9rem;
    line-height: 1.4;
    word-wrap: break-word;
    animation: msgIn 0.5s ease both;
}

.message.received {
    align-self: flex-start;
    background: #fff;
    color: var(--text-primary);
    border-bottom-left-radius: 6px;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.08);
}

.message.sent {
    align-self: flex-end;
    background: var(--tg-blue-gradient);
    color: #fff;
    border-bottom-right-radius: 6px;
}

.message:nth-child(1) { animation-delay: 0.2s; }
.message:nth-child(2) { animation-delay: 0.5s; }
.message:nth-child(3) { animation-delay: 0.8s; }
.message:nth-child(4) { animation-delay: 1.1s; }

@keyframes msgIn {
    from {
        opacity: 0;
        transform: translateY(10px) scale(0.95);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.wave {
    position: absolute;
    bottom: -1px;
    left: 0;
    right: 0;
    height: 80px;
    background: var(--bg-white);
    border-radius: 50% 50% 0 0 / 100% 100% 0 0;
}

/* ===== 章节标题 ===== */
.section-header {
    text-align: center;
    margin-bottom: 64px;
}

.section-header h2 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 16px;
    letter-spacing: -0.01em;
}

.section-header p {
    font-size: 1.125rem;
    color: var(--text-secondary);
}

/* ===== 下载区 ===== */
.download {
    background: var(--bg-white);
}

.platform-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.platform-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 36px 28px;
    text-align: center;
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.platform-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--tg-blue-gradient);
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.platform-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-md);
    border-color: transparent;
}

.platform-card:hover::before {
    transform: scaleX(1);
}

.platform-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    background: var(--bg-light);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--tg-blue-dark);
    transition: all 0.3s ease;
}

.platform-icon svg {
    width: 32px;
    height: 32px;
}

.platform-card:hover .platform-icon {
    background: var(--tg-blue-gradient);
    color: #fff;
    transform: rotate(8deg);
}

.platform-card h3 {
    font-size: 1.3rem;
    font-weight: 700;
    margin-bottom: 6px;
}

.platform-card p {
    color: var(--text-light);
    font-size: 0.9rem;
    margin-bottom: 20px;
}

.platform-btn {
    display: inline-block;
    padding: 10px 24px;
    background: var(--bg-light);
    color: var(--tg-blue-dark);
    border-radius: 50px;
    font-size: 0.875rem;
    font-weight: 600;
    transition: all 0.3s ease;
}

.platform-card:hover .platform-btn {
    background: var(--tg-blue-gradient);
    color: #fff;
}

.platform-card-web {
    grid-column: span 1;
}

/* ===== 功能区 ===== */
.features {
    background: var(--bg-light);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.feature-card {
    background: var(--bg-white);
    border-radius: var(--radius-md);
    padding: 36px 28px;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    text-align: left;
}

.feature-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.feature-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius-sm);
    background: var(--tg-blue-gradient);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
}

.feature-icon svg {
    width: 28px;
    height: 28px;
}

.feature-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.feature-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* ===== CTA ===== */
.cta {
    background: var(--tg-blue-gradient);
    color: #fff;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.cta::before, .cta::after {
    content: '';
    position: absolute;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.08);
}

.cta::before {
    width: 400px;
    height: 400px;
    top: -200px;
    left: -100px;
}

.cta::after {
    width: 300px;
    height: 300px;
    bottom: -150px;
    right: -80px;
}

.cta-content {
    position: relative;
    z-index: 1;
    max-width: 700px;
    margin: 0 auto;
}

.cta-content h2 {
    font-size: 2.75rem;
    font-weight: 800;
    margin-bottom: 16px;
}

.cta-content p {
    font-size: 1.2rem;
    opacity: 0.95;
    margin-bottom: 36px;
}

.cta .btn-primary {
    background: #fff;
    color: var(--tg-blue-dark);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.cta .btn-primary:hover {
    background: #f5f8fc;
}

/* ===== FAQ ===== */
.faq {
    background: var(--bg-white);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.faq-item {
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--bg-white);
    overflow: hidden;
    transition: all 0.3s ease;
}

.faq-item.active {
    border-color: var(--tg-blue);
    box-shadow: var(--shadow-md);
}

.faq-question {
    width: 100%;
    background: none;
    border: none;
    padding: 22px 28px;
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-primary);
    text-align: left;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: color 0.2s ease;
}

.faq-item.active .faq-question {
    color: var(--tg-blue-dark);
}

.faq-icon {
    position: relative;
    width: 18px;
    height: 18px;
    flex-shrink: 0;
    margin-left: 16px;
}

.faq-icon::before,
.faq-icon::after {
    content: '';
    position: absolute;
    background: currentColor;
    border-radius: 2px;
    transition: transform 0.3s ease;
}

.faq-icon::before {
    top: 50%;
    left: 0;
    width: 18px;
    height: 3px;
    transform: translateY(-50%);
}

.faq-icon::after {
    top: 0;
    left: 50%;
    width: 3px;
    height: 18px;
    transform: translateX(-50%);
}

.faq-item.active .faq-icon::after {
    transform: translateX(-50%) scaleY(0);
}

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.4s ease, padding 0.3s ease;
    padding: 0 28px;
}

.faq-item.active .faq-answer {
    max-height: 300px;
    padding-bottom: 22px;
}

.faq-answer p {
    color: var(--text-secondary);
    font-size: 0.98rem;
}

/* ===== 页脚 ===== */
.footer {
    background: #1a1a1a;
    color: #c7c7c7;
    padding: 64px 0 24px;
}

.footer-content {
    display: grid;
    grid-template-columns: 1.5fr 2fr;
    gap: 60px;
    margin-bottom: 48px;
}

.footer-brand .logo {
    color: #fff;
    margin-bottom: 16px;
}

.footer-brand p {
    color: #8a8a8a;
    font-size: 0.95rem;
    max-width: 280px;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.footer-col h4 {
    color: #fff;
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 18px;
}

.footer-col ul {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.footer-col a {
    color: #8a8a8a;
    font-size: 0.92rem;
    transition: color 0.2s ease;
}

.footer-col a:hover {
    color: var(--tg-blue-light);
}

.footer-bottom {
    border-top: 1px solid #2a2a2a;
    padding-top: 24px;
    text-align: center;
}

.footer-bottom p {
    color: #6a6a6a;
    font-size: 0.85rem;
}

/* ===== 响应式 ===== */
@media (max-width: 992px) {
    .hero-content {
        grid-template-columns: 1fr;
        gap: 40px;
        text-align: center;
    }

    .hero-text h1 {
        font-size: 2.8rem;
    }

    .hero-subtitle {
        margin-left: auto;
        margin-right: auto;
    }

    .hero-buttons, .hero-stats {
        justify-content: center;
    }

    .platform-grid,
    .features-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .footer-content {
        grid-template-columns: 1fr;
        gap: 40px;
    }
}

@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        top: var(--header-height);
        left: 0;
        right: 0;
        flex-direction: column;
        background: #fff;
        padding: 24px;
        gap: 8px;
        box-shadow: var(--shadow-md);
        transform: translateY(-150%);
        transition: transform 0.3s ease;
    }

    .nav-links.active {
        transform: translateY(0);
    }

    .nav-links li {
        width: 100%;
    }

    .nav-links a {
        display: block;
        padding: 12px 8px;
        font-size: 1rem;
        border-radius: 8px;
    }

    .nav-links a:hover {
        background: var(--bg-light);
    }

    .nav-links a::after {
        display: none;
    }

    .menu-toggle {
        display: flex;
    }

    .section {
        padding: 70px 0;
    }

    .hero-text h1 {
        font-size: 2.2rem;
    }

    .hero-subtitle {
        font-size: 1.05rem;
    }

    .section-header h2 {
        font-size: 2rem;
    }

    .section-header p {
        font-size: 1rem;
    }

    .phone-mockup {
        width: 260px;
        height: 520px;
    }

    .platform-grid,
    .features-grid {
        grid-template-columns: 1fr;
    }

    .footer-links {
        grid-template-columns: repeat(2, 1fr);
    }

    .cta-content h2 {
        font-size: 2rem;
    }

    .cta-content p {
        font-size: 1rem;
    }

    .btn-lg {
        padding: 16px 36px;
        font-size: 1rem;
    }
}

@media (max-width: 480px) {
    .hero {
        padding-bottom: 40px;
    }

    .hero-text h1 {
        font-size: 1.85rem;
    }

    .hero-buttons {
        flex-direction: column;
        width: 100%;
    }

    .btn {
        width: 100%;
    }

    .hero-stats {
        gap: 24px;
    }

    .stat strong {
        font-size: 1.4rem;
    }

    .phone-mockup {
        width: 220px;
        height: 440px;
    }

    .footer-links {
        grid-template-columns: 1fr;
    }
}

/* ===== 子页面共享样式 ===== */

/* 页面标题区（download / features / faq） */
.page-hero {
    padding-top: calc(var(--header-height) + 80px);
    padding-bottom: 40px;
    background: linear-gradient(180deg, #f5f8fc 0%, #ffffff 100%);
    text-align: center;
}

.page-hero h1 {
    font-size: 2.8rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    margin-bottom: 16px;
}

.page-hero p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    max-width: 640px;
    margin: 0 auto;
}

/* 首页概览卡片 */
.overview {
    background: var(--bg-white);
}

.overview-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.overview-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 36px 28px;
    transition: all 0.3s ease;
    text-align: left;
    position: relative;
    overflow: hidden;
}

.overview-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--tg-blue-gradient);
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.overview-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-md);
    border-color: transparent;
}

.overview-card:hover::before {
    transform: scaleX(1);
}

.overview-icon {
    width: 56px;
    height: 56px;
    border-radius: var(--radius-sm);
    background: var(--bg-light);
    color: var(--tg-blue-dark);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
    transition: all 0.3s ease;
}

.overview-icon svg {
    width: 28px;
    height: 28px;
}

.overview-card:hover .overview-icon {
    background: var(--tg-blue-gradient);
    color: #fff;
}

.overview-card h3 {
    font-size: 1.3rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.overview-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-bottom: 16px;
}

.overview-link {
    color: var(--tg-blue-dark);
    font-weight: 600;
    font-size: 0.95rem;
    transition: transform 0.2s ease;
    display: inline-block;
}

.overview-card:hover .overview-link {
    transform: translateX(4px);
}

/* 安装步骤 */
.install {
    background: var(--bg-light);
}

.install-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
    counter-reset: step;
}

.install-step {
    text-align: center;
    padding: 0 12px;
}

.step-number {
    width: 56px;
    height: 56px;
    margin: 0 auto 20px;
    border-radius: 50%;
    background: var(--tg-blue-gradient);
    color: #fff;
    font-size: 1.5rem;
    font-weight: 800;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 8px 20px rgba(42, 171, 238, 0.3);
}

.install-step h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 10px;
}

.install-step p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.6;
}

/* 详细功能（features.html）*/
.detail {
    background: var(--bg-white);
}

.detail-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.detail-item {
    background: var(--bg-light);
    border-radius: var(--radius-md);
    padding: 28px 24px;
    border-left: 4px solid var(--tg-blue);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.detail-item:hover {
    transform: translateX(4px);
    box-shadow: var(--shadow-sm);
}

.detail-item h3 {
    font-size: 1.15rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.detail-item p {
    color: var(--text-secondary);
    font-size: 0.92rem;
    line-height: 1.6;
}

.detail-block {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 32px 28px;
    margin-bottom: 24px;
    transition: box-shadow 0.3s ease;
}

.detail-block:hover {
    box-shadow: var(--shadow-sm);
}

.detail-block h3 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 12px;
}

.detail-block p {
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 14px;
}

.detail-block ul {
    padding-left: 20px;
    color: var(--text-secondary);
    line-height: 1.9;
}

.detail-block ul li {
    margin-bottom: 6px;
}

.detail-block a {
    color: var(--tg-blue);
    text-decoration: none;
    font-weight: 500;
}

.detail-block a:hover {
    text-decoration: underline;
}

/* 联系卡片（faq.html）*/
.contact {
    background: var(--bg-light);
}

.contact-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.contact-card {
    background: var(--bg-white);
    border-radius: var(--radius-md);
    padding: 32px 24px;
    text-align: center;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    border: 1px solid transparent;
}

.contact-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    border-color: var(--tg-blue);
}

.contact-card h3 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.contact-card p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

/* 导航激活状态 */
.nav-links a.active {
    color: var(--tg-blue-dark);
    font-weight: 600;
}

.nav-links a.active::after {
    width: 100%;
}

/* 响应式：子页面 */
@media (max-width: 992px) {
    .overview-grid,
    .install-grid,
    .detail-grid,
    .contact-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .page-hero h1 {
        font-size: 2.2rem;
    }
}

@media (max-width: 768px) {
    .overview-grid,
    .install-grid,
    .detail-grid,
    .contact-grid {
        grid-template-columns: 1fr;
    }

    .page-hero {
        padding-top: 30px;
    }

    .page-hero h1 {
        font-size: 1.9rem;
    }

    .page-hero p {
        font-size: 1rem;
    }
}

/* ===== 各平台安装指南（download.html）===== */
.guides {
    background: var(--bg-light);
}

.guides-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.guide-card {
    background: var(--bg-white);
    border-radius: var(--radius-md);
    padding: 32px 28px;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
    border-top: 4px solid var(--tg-blue);
}

.guide-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
}

.guide-card h3 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 16px;
    color: var(--tg-blue-dark);
}

.guide-card ol {
    display: flex;
    flex-direction: column;
    gap: 10px;
    padding-left: 20px;
    counter-reset: guide-step;
}

.guide-card ol li {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.6;
    counter-increment: guide-step;
}

.guide-card ol li::marker {
    color: var(--tg-blue);
    font-weight: 700;
}

/* ===== 系统要求表格（download.html）===== */
.requirements {
    background: var(--bg-white);
}

.requirements-table {
    overflow-x: auto;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border-color);
}

.requirements-table table {
    width: 100%;
    border-collapse: collapse;
    min-width: 640px;
}

.requirements-table thead {
    background: var(--tg-blue-gradient);
    color: #fff;
}

.requirements-table th {
    padding: 16px 20px;
    text-align: left;
    font-weight: 700;
    font-size: 0.95rem;
    white-space: nowrap;
}

.requirements-table td {
    padding: 14px 20px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.92rem;
}

.requirements-table tbody tr:last-child td {
    border-bottom: none;
}

.requirements-table tbody tr:hover {
    background: var(--bg-light);
}

.requirements-table tbody tr td:first-child {
    font-weight: 700;
    color: var(--text-primary);
}

/* 安装指南 / 系统要求响应式 */
@media (max-width: 992px) {
    .guides-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .guides-grid {
        grid-template-columns: 1fr;
    }

    .requirements-table th,
    .requirements-table td {
        padding: 12px 14px;
        font-size: 0.85rem;
    }
}

/* ===== 面包屑导航 ===== */
.breadcrumb {
    padding-top: calc(var(--header-height) + 24px);
    padding-bottom: 12px;
    background: var(--bg-light);
}

.breadcrumb-list {
    list-style: none;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 8px;
    font-size: 0.9rem;
    color: var(--text-light);
}

.breadcrumb-list li {
    display: flex;
    align-items: center;
    gap: 8px;
}

.breadcrumb-list li + li::before {
    content: "/";
    color: var(--text-light);
    opacity: 0.6;
}

.breadcrumb-list a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.2s ease;
}

.breadcrumb-list a:hover {
    color: var(--tg-blue);
}

.breadcrumb-current {
    color: var(--tg-blue-dark);
    font-weight: 600;
}

/* ===== 首页介绍区 ===== */
.intro {
    background: var(--bg-light);
}

.intro-content {
    max-width: 860px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.intro-content p {
    color: var(--text-secondary);
    font-size: 1.02rem;
    line-height: 1.9;
    text-align: justify;
}

.intro-content p:first-child::first-letter {
    font-size: 2rem;
    font-weight: 800;
    color: var(--tg-blue-dark);
    float: left;
    line-height: 1;
    margin-right: 6px;
    margin-top: 4px;
}

@media (max-width: 768px) {
    .intro-content p {
        font-size: 0.95rem;
        line-height: 1.8;
    }

    .intro-content p:first-child::first-letter {
        font-size: 1.6rem;
    }
}

/* ===== 首页使用教程与评测板块 ===== */
.tutorials {
    background: var(--bg-light);
}

.tutorial-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
}

.tutorial-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 32px 28px;
    transition: all 0.3s ease;
    text-align: left;
    position: relative;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.tutorial-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-md);
    border-color: transparent;
}

.tutorial-badge {
    display: inline-block;
    padding: 4px 12px;
    background: rgba(42, 171, 238, 0.1);
    color: var(--tg-blue-dark);
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 16px;
    align-self: flex-start;
}

.tutorial-card h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 12px;
    line-height: 1.4;
}

.tutorial-card > p {
    color: var(--text-secondary);
    font-size: 0.95rem;
    line-height: 1.7;
    margin-bottom: 16px;
    flex-grow: 1;
}

.tutorial-meta {
    display: flex;
    gap: 16px;
    margin-bottom: 16px;
    font-size: 0.82rem;
    color: var(--text-light);
}

.tutorial-card .overview-link {
    margin-top: auto;
}

@media (max-width: 992px) {
    .tutorial-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    .tutorial-grid {
        grid-template-columns: 1fr;
    }
}

/* ===== 文章内容页（comparison / secret-chat）===== */
.article {
    background: var(--bg-white);
    padding-top: 40px;
    padding-bottom: 80px;
}

.article-container {
    max-width: 820px;
    margin: 0 auto;
    padding: 0 24px;
}

.article-meta {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 32px;
    color: var(--text-light);
    font-size: 0.9rem;
}

.article-meta .article-tag {
    padding: 4px 12px;
    background: rgba(42, 171, 238, 0.1);
    color: var(--tg-blue-dark);
    border-radius: 20px;
    font-weight: 600;
}

.article-body {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.article-body h2 {
    font-size: 1.6rem;
    font-weight: 700;
    margin-top: 16px;
    padding-bottom: 12px;
    border-bottom: 2px solid var(--bg-light);
}

.article-body h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-top: 8px;
    color: var(--tg-blue-dark);
}

.article-body p {
    color: var(--text-secondary);
    font-size: 1.02rem;
    line-height: 1.9;
    text-align: justify;
}

.article-body ul,
.article-body ol {
    padding-left: 24px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.article-body ul li,
.article-body ol li {
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.8;
}

.article-body ul li::marker {
    color: var(--tg-blue);
}

.article-body ol li::marker {
    color: var(--tg-blue);
    font-weight: 700;
}

.article-body table {
    width: 100%;
    border-collapse: collapse;
    margin: 8px 0;
    box-shadow: var(--shadow-sm);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.article-body thead {
    background: var(--tg-blue-gradient);
    color: #fff;
}

.article-body th {
    padding: 14px 16px;
    text-align: left;
    font-weight: 700;
    font-size: 0.95rem;
}

.article-body td {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.article-body tbody tr:last-child td {
    border-bottom: none;
}

.article-body tbody tr:hover {
    background: var(--bg-light);
}

.article-body blockquote {
    border-left: 4px solid var(--tg-blue);
    background: var(--bg-light);
    padding: 16px 24px;
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    color: var(--text-secondary);
    font-style: italic;
    line-height: 1.8;
}

.article-body .highlight {
    background: linear-gradient(120deg, rgba(42, 171, 238, 0.15) 0%, rgba(42, 171, 238, 0.15) 100%);
    padding: 2px 6px;
    border-radius: 4px;
    font-weight: 600;
}

.article-body .callout {
    background: rgba(42, 171, 238, 0.06);
    border: 1px solid rgba(42, 171, 238, 0.2);
    border-radius: var(--radius-sm);
    padding: 18px 22px;
}

.article-body .callout strong {
    color: var(--tg-blue-dark);
}

.article-cta {
    margin-top: 48px;
    padding: 36px;
    background: var(--bg-light);
    border-radius: var(--radius-md);
    text-align: center;
}

.article-cta h3 {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 12px;
}

.article-cta p {
    color: var(--text-secondary);
    margin-bottom: 20px;
}

@media (max-width: 768px) {
    .article-body h2 {
        font-size: 1.3rem;
    }

    .article-body h3 {
        font-size: 1.1rem;
    }

    .article-body p,
    .article-body ul li,
    .article-body ol li {
        font-size: 0.95rem;
    }

    .article-body th,
    .article-body td {
        padding: 10px 12px;
        font-size: 0.88rem;
    }
}